DE102006062354A1 - Drive arrangement for a portable working device - Google Patents

Abstract

It is proposed a drive arrangement (20) for a hand-held implement (10) for landscaping, forestry and horticulture, with an electric motor (M), a memory (A) for electrical energy and a control device (S) for the from Energy storage (A) powered electric motor (M), wherein the electric motor (M) has a specific, in particular linear characteristic (30) between the electric motor (M) recorded electrical current (i) and the rotational speed (w) of an output shaft (22) of the electric motor (M), the control device (S) having current limiting means (26) limiting the current (i) flowing through the electric motor (M) to a maximum value in order to protect the electric motor (M) from overloading. In this case, the control device (S) limits the current consumption of the electric motor (M) in a range of low rotational speeds as a function of the rotational speed to values that are significantly smaller than the characteristic values which for these rotational speeds from the characteristic curve (30) of the electric motor (M ).

Description

The The present invention relates to a drive arrangement for a mobile, especially hand-held or portable work equipment for the Landscape, forestry and horticulture, with an electric motor, a Memory for electrical energy, and a control device for the off the electric energy-powered electric motor, wherein the electric motor a certain, in particular linear characteristic between that of the electric motor absorbed electric current and the rotational speed of an output shaft of the electric motor, wherein the control device current limiting means comprising the current flowing through the electric motor to a maximum value limit to protect the electric motor from overloading.

The The present invention further relates to a corresponding method for controlling an electric motor and a hand-held implement for landscaping, Forestry and horticulture with such a drive arrangement.

On Almost all areas of electrical engineering are well-known means to use current limiting, current carrying components from overloading to protect. These current limiting devices only come into effect when the current exceeds certain predetermined limits (eg due to the failure of other components, due to incorrect operation, Etc.). In other words, the current is usually independent of the applied voltage and / or independent of the respective electrical Resistance limited to a maximum value.

From the document DE 34 22 485 A1 It is known to apply a temperature-compensated current limiting in an electric motor, which is intended for driving hand tools and the like. Here it is proposed to measure the electric current flowing through the motor by means of a series current. On the other hand, the temperature of the row shunt is measured via an NTC resistor. From the temperature of the series Hunts the temperature of the electric motor is detected indirectly. When a critical motor temperature is reached, the power supply is continuously, but felt by the user, withdrawn. In response, the user puts the tool free of load so that the electric motor can cool down quickly.

In the field of equipment for landscaping, forestry and horticulture such devices are known, which are driven by an internal combustion engine. These devices are often used in the professional field. Furthermore, such implements are known, which are electrically powered. It is known in particular in the field of private applications to feed the electric motor from the grid. This requires a connection of a stationary power plug to the implement via a cable. Such devices are generally not suitable for the professional sector, since a power plug is not available at a reasonable distance. In the case of electrically driven implements, likewise in the field of private use and in the professional field, such implements are known which are fed from an electrical energy store (eg NiCd accumulator). For some years, however, lithium-based batteries have also been used. Such accumulators are generally also suitable for professional tools, see WO 2005/053915 , In this document, it is proposed to use a current limiter to protect a lithium-based battery.

In front In the above background, it is the object of the invention to provide an improved Drive arrangement for a hand-held Implement, an improved method for controlling an electric motor for such Drive arrangement and an improved hand-held implement for landscape, Indicate forestry and horticulture.

These Task is characterized by the drive assembly mentioned above solved, that the control device, the current consumption of the electric motor in a range of low speeds generally limited to value, the are significantly smaller than the characteristic values that are suitable for this Speeds resulting from the characteristic of the electric motor.

electric motors generally have a characteristic that at low speeds a high power consumption and at high speeds low power consumption shows. A high current consumption usually means as well a high, output from the electric motor torque.

combustion engines have in contrast a characteristic that is relatively low at low speeds Torque provides, in a medium speed range relatively high torque, and in a range of high speeds again a relatively low torque.

As a general rule is the characteristic of electric motors, lower in areas Speeds high moments available to ask, quite desirable.

With the present invention, however, it is proposed to limit the current consumption in general, ie independently of other parameters, especially in the region of low rotational speeds. With ande Ren words, the control device to the electric motor to a new characteristic, which causes a lower power consumption in the range of low speeds.

This As a result, that of the implement in the range of low speeds to disposal Asked torque is generally smaller than it is used by the Electric motor possible would. Although this seems disadvantageous at first glance, is hereby a Series of advantages.

at implements for the Landscaping, forestry and horticulture are the work tools often on a rated speed controlled. On the other hand, the load for the electric motor changes constantly, and for example, due to changed Behavior of the user, due to changed circumstances (eg thick branches / thin branches, etc.).

Becomes the load is greatly increased, the speed of the motor decreases. This leads to a relatively strong Current increase and thus to a relatively high power consumption. This reduces the operating time of the portable energy storage. Further reduces the efficiency of the engine.

By the "active" current limit in the range of low speeds is thus achieved that the Power consumption is reduced in such situations. This extends the Operating time of the energy storage. Furthermore, the user gets a better "feedback" when he gets one too size Force on the implement exercises. In conventional Drive arrangements with electric motor show this to the user less strong, because the electric motor in the low-speed range then a higher torque provides. In contrast receives the user of a working device with a drive assembly of the present invention a better Reaction to his behavior.

All in all This can also be prevented that the electric motor to quickly overheated. The general limitation of power consumption can be a conventional Replace current limit to a maximum current. It goes without saying however, that too an extra Current limiting device for preventing overloading the electric motor may be present, for example, a fuse or similar. The maximum current of such an additional current limiting device is however, usually higher than that of the general invention Current limiters approved maximum current.

The Limitation of power consumption in the range of low speeds takes place according to the invention in dependence from the speed. In other words, the power consumption is within this Range of low speeds not to a single fixed current value limited. Rather, the current limit can be within this range be different pronounced at different speeds. The control characteristic generated thereby can thus in the area low speeds have a non-zero slope, or a plurality of sections with different gradients. Also not linear control curve sections in this area are feasible.

Further allows the invention, the performance characteristics of the implement application optimal adjust.

The The above object is further by a corresponding method for Controlling an electric motor and by a hand-held implement with a Drive arrangement according to the invention solved.

As mentioned, the limitation of the current consumption in the area is lower Speed generally, ie essentially independent of other operating parameters the drive assembly.

Especially should the general limitation of power consumption regardless of the temperature of the electric motor done.

According to one another preferred embodiment the control device divides the from the characteristic of the electric motor predetermined speed range in a plurality of at least three Speed ranges, wherein at least in a medium speed range a control characteristic section with a smaller slope than the characteristic of the electric motor is set up.

at this embodiment becomes an "active" current limit already set up in a medium speed range.

hereby let yourself the control characteristic of the control device in the central region For example, qualitatively and / or quantitatively to the characteristic of a Adjust combustion engine. This allows operation of a certain type of work equipment, independently of whether the device by a drive arrangement according to the invention is driven or by a drive assembly with internal combustion engine. The user therefore does not have to work in different ways to adjust.

in this connection is of particular advantage when in a lower speed range a control characteristic section is set up with a slope, which is smaller than the slope of the control characteristic section in the middle speed range.

This allows a relatively stronger active Current limitation at low speeds than at medium speeds.

Further can be achieved that the current limit of the control curve section approximate to control curve section change continuously leaves. You can set up a steady control curve history so that a jerk-free operation of the implement is possible.

According to one particularly preferred embodiment is the slope of the control characteristic section in the lower Speed range zero.

On this way can for the range of very low speeds of electricity are relatively severely limited, such an overload of the motor or an excessive power extraction from the portable Counteract energy storage.

The Control characteristic sections can generally have any shape, but are each preferably formed linear. Generally, the control curve ranges have prefers a positive slope or a slope of zero. in the Range of very low speeds, however, it is also generally conceivable to set up a negative slope control map section.

All in all It is further preferred if in an upper speed range in There is essentially no limitation on the power consumption.

There that is available in this area Torque is relatively low anyway due to the low currents, Because of the characteristic of the electric motor is in this Area preferably no limitation of power consumption performed.

All in all It is further preferred if the control device, the power consumption the electric motor at least in the range of low speeds generally limited to values that are at least 20% smaller than the characteristic values that are suitable for these speeds result from the characteristic of the electric motor.

hereby An effective energy saving is realized in this speed range.

Preferably the control characteristic is in total adapted to the respective application of the working device adjusted so that with the same electric motor and different Work tools different Can give control characteristics.

Further it is preferred if the current is due to a voltage regulation is limited. The reference variable can either be a measured speed or a map, the for every electric motor is characteristic.

at the method according to the invention it is preferred if the current limit is optimal efficiency. In other words, that means by the nature of the current limit the overall efficiency of the hand-held implement improved is, so overall a longer one Operating time achievable with a given accumulator charge is.

Further the user can over the current limit and the torque curve are so "led" that he the device operating at or near optimum efficiency.

According to one another preferred embodiment includes the control characteristic generated by the current limitation in the field of current limiting a hysteresis section.

With In other words, the limitation of the current takes place within the hysteresis section different depending of whether the speed increases is or is reduced.

Especially it is advantageous in this case if the hysteresis section is designed in this way is that while raising the speed of a relatively high current is absorbed and that at Decreasing the speed added a relatively lower power becomes.

With In other words, this can be achieved by reducing the speed (for example due to a higher load) the power consumption relatively strong is, so that significant energy savings can be achieved.

If on the other hand increases the speed is, for example, when starting the electric motor from a standstill, can be used in some applications (for example, chainsaw or Hedge shears) a high breakaway torque may be desired, so that when increasing the Speed only a relatively small current limit is performed.

According to one another embodiment includes the control characteristic generated by the current limitation in the area of the current limit, a section where the control characteristic has a negative slope.

In this embodiment, the control characteristic is more closely approximated to the typical characteristic of an internal combustion engine, which usually has a maximum torque even in a medium speed range and especially in the range of low speeds only a smaller Can provide torque.

By This measure can also be achieved that the behavior of the hand-held implement for the user represents largely uniform, regardless of whether the working device of a Internal combustion engine is driven or by an electric motor.

alternative this is also possible that the control characteristic generated by the current limitation in the range the current limit includes a breakaway section, in the at the startup of the electric motor from standstill a very high Electricity is absorbed.

As mentioned above, Such a breakaway torque generated by this can for some Applications be very beneficial. Generally, the breakaway section relatively narrow, so that actually only at very low Speeds a high breakaway torque is provided at all however, other speeds in the control map section Efficiency-optimal current limit is feasible.

The Speed of the electric motor, depending on which the limit The current consumption takes place, for example, by means of a speed sensor be measured.

Prefers However, it is when the speed of the electrical quantities of Electric motor such as the voltage and / or absorbed by the electric motor electric current is derived.

at this embodiment a separate speed sensor is not required.

It it is understood that the above and the following yet to be explained features not only in the specified combination, but also in other combinations or alone, without to leave the scope of the present invention.

embodiments The invention are illustrated in the drawings and in the following description explained. Show it:

1 a schematic representation of a working device for landscaping, forestry and horticulture with a drive assembly according to the invention;

2 a diagram of current over speed with representation of a characteristic of an electric motor, a characteristic of an internal combustion engine and a control characteristic according to the invention;

3 one of the 2 corresponding diagram showing different control characteristics according to the invention;

4 a further diagram showing an alternative control characteristic according to the invention with a hysteresis section;

5 a further diagram showing the control characteristics of the invention.

In 1 is a working implement for landscaping, forestry or horticulture schematically with 10 designated.

The working device 10 has a tool 12 on, in the present case schematically as a knife 14 a hedge trimmer is indicated, and a drive assembly, which generally with 20 is designated.

The work tool can, as by the knife 14 implied to be a hedge trimmer. Other examples of equipment according to the invention 10 are brush cutters, lawn edge cutters, chainsaws, earth boring machines, blowers, vacuum choppers, brushcutters, cut-off sanders, suction devices (wet or dry), sprayers and blowers, high-pressure cleaners, lawnmowers, etc.

The working device 10 is preferably designed as a hand-held implement that can be carried or guided by an operator. Generally, the implement is 10 designed for professional use.

The drive arrangement 20 has an electric motor M, a control device S and an electrical energy storage in the form of a rechargeable and replaceable battery pack A.

The energy store A provides a supply voltage U _A , namely for the control device S. The control device S supplies the electric motor M with an electric current i. The electric motor M has an output shaft 22 on. The output shaft 22 is either directly with the tool 12 coupled or via any transducer, such as a rotational-translation converter, a reduction gear, and / or the like. Such a transducer is in 1 schematically at 24 shown.

The control device S has on the one hand a per se known power electronics 28 for driving the electric motor M on. The power electronics 28 may also be formed separately from the control device S. Furthermore, the control device S current limiting means 26 on.

The current limiters 26 serve to impart a control characteristic to the electric motor M, in which the power consumption of the electric motor M is generally limited in the range of low and possibly average rotational speeds. The current limiters 26 receive on the input side, the output voltage U _A. Furthermore, the current limiting means 26 with information about the speed n of the output shaft 22 provided.

The current limiters 26 For example, the control characteristic can be impressed on the electric motor M in any manner. Preferably, this is done by a voltage control, which may include, for example, the speed n as a reference variable.

alternative Is it possible, in the control device S store a map that for the respective Electric motor M is characteristic and fixed relationships between Set up speed, current and voltage.

2 shows a diagram of motor current i over the speed n. In the diagram of 2 is on the one hand a characteristic motor characteristic 30 applied to the electric motor M. The motor characteristic 30 is a common characteristic of an electric motor and runs substantially linearly from a relatively high current at low speeds to a low current at high speeds.

In 2 is also dotted the characteristic 32 an internal combustion engine, as it is typically used in implements for landscaping, forestry or horticulture. An internal combustion engine can only deliver a torque above a certain idle speed, which is initially relatively low in the region of the idling speed. In the range of average speeds, the torque then increases slightly and drops again at high speeds. At high speeds, the characteristic curve 32 of the internal combustion engine substantially the characteristic 30 of the electric motor M correspond. At medium and low speeds are the characteristics of the curves 30 . 32 but completely different. In an electric motor, the energy requirement and consequently the torque provided increases sharply at low speeds. In an internal combustion engine, the torque provided falls off at low speeds. In this context it is understood that for the characteristic curve 32 the y-axis corresponds to the torque output by the internal combustion engine, that is, for example, is proportional to the throttle position. For a typical electric motor, the motor current is also proportional to the specified torque.

The current limiters 26 Now, the electric motor M is characterized by a control characteristic which, in 2 With 34 is designated.

The control characteristic 34 is composed of a plurality of control characteristic sections. Here is the of the motor characteristic 30 covered speed range divided into a plurality of individual speed ranges, namely a first speed range 36 , which includes low speeds, a second speed range 38 that involves slightly higher speeds, a third speed range 40 that is related to the speed range 38 connects and includes medium speeds, a fourth speed range 42 that is related to the speed range 40 connects and also includes average speeds, and a fifth speed range 44 that is at the fourth speed range 42 connects and higher speeds up to the maximum speed includes.

In the first speed range 36 indicates the control characteristic 34 a control characteristic section 37 which is formed linearly, with a slope of zero. The control curve section 37 represents the maximum motor current i _max , the z. B. at least 15%, 20% or 30% below the current, in this speed range 36 with the normal characteristic 30 would be realized.

In the second speed range 38 indicates the control characteristic 34 a second control characteristic section 38 on, which is formed linearly, with a slope corresponding approximately to the slope of the motor characteristic 30 , In the third speed range 40 indicates the control characteristic 34 a third control characteristic section 41 which in turn is formed linearly, with a slope which is significantly lower than the slope of the motor characteristic 30 , In the fourth speed range 42 indicates the control characteristic 34 a control characteristic section 43 on, which in turn is linear. The fourth control curve section 43 has a slope between the slope of the control curve section 41 and that of the control line section 39 lies.

It is understood in the present context that in the comparison the gradients generally meant the amount of the respective gradients is.

In the fifth speed range 44 indicates the control characteristic 34 a control characteristic section 45 which is identical to the corresponding section of the motor characteristic 30 ,

In other words, the motor current i by means of the impressed control characteristic 34 in the fifth speed range 44 not limited at all. In the fourth speed range 42 the motor current i is somewhat limited in relative terms. In the third speed range 40 the motor current i is seen relatively more limited. In the second speed range 38 takes place, relatively speaking, again a slightly lower current limit. In the first speed range 36 is the motor current i constant limited to a fixed value i _max , so relatively speaking relatively strong.

Through the control characteristic 34 Therefore, the motor current i is "active" limited to reduce power consumption, especially at low speeds, and "feedback" can be given to the user remotely when "overprinting" the implement.

In addition, the efficiency of an electric motor M in the low-speed range is generally slightly lower. Consequently, by the control characteristic according to the invention 34 the power consumption can be reduced, the efficiency of the implement 10 be increased overall. Furthermore, in particular the duration of use of the energy store A can be extended.

All this is done by an electronic limitation of the motor current to a suitable moment identifier, which may for example depend on the typical application of the implement. The control characteristic 34 of the 2 is therefore only to be understood as an example.

In 3 are in turn next to a motor characteristic 30 two alternative control curves 34 ^I respectively. 34 ^II shown.

The control characteristic 34 ^I is in five control line sections 37 ^I . 39 ^I . 41 ^I . 43 ^I . 45 ^I subdivided - qualitatively essentially comparable to the control characteristic 34 of the 2 ,

The control characteristic 34 ^II is divided over the available speed range in only three speed ranges, with a first control characteristic section 37 ^II in which the motor current i is limited to a fixed value, with a last control characteristic section 45 ^II in which the control characteristic 34 ^II the motor characteristic 30 corresponds, and in a middle control curve section 39 ^II , which has a slightly lower slope than the engine characteristic 30 having.

Generally applies to the control curves 34 . 34 ^I . 34 ^II A. In a medium speed range, the control characteristic 34 preferably the characteristic of the internal combustion engine 32 approximated. Although in a range of low speeds, the general advantage of the electric motor M is still used, to the extent that it can generally provide relatively high torques in the low-speed range. However, a relatively high current limit is already being implemented in this area. As a result, the operating time of the energy storage A, ie the time until it is discharged and must be recharged, relatively extended.

In the 4 and 5 Further alternative embodiments of control characteristics according to the invention are shown. For these, the above applies to the control characteristics already described. In the following, however, special features of the control characteristics explained below are discussed.

In 4 is a control characteristic 34 ^III shown having a control characteristic section 45 ^III and a first current limiting control characteristic section 41 ^III having. Further, a second current limiting control characteristic section is a hysteresis section 37a ^III . 37b ^III educated. The hysteresis portion is designed so that when increasing the speed of a relatively high current 37b ^III is recorded. Reducing the speed becomes a relatively lower current 37a ^III added.

It it is understood that such a hysteresis section preferably, however, not necessarily at speed limits with speed Zero adjoins. Furthermore, it is advantageous, but not essential necessary, that if, when starting a relatively high torque is provided, the maximum current at zero speed maximum of the electric motor M output current corresponds.

In general, the hysteresis section can also be designed so that when starting generally the normal characteristic 30 the electric motor is "used", and current limiting occurs only in the reverse direction in reducing the speed.

In 5 are two more control characteristics according to the invention 34 ^IV . 34 ^v shown.

The control characteristic 34 ^IV has a first, "normal" control curve section 41 ^IV and a second control characteristic section 37 ^IV in which the slope of the control characteristic 34 ^IV is negative.

The control characteristic 34 ^IV Therefore, in its form generally corresponds to the shape of the characteristic of an internal combustion engine, as in 2 at 32 is shown.

The control characteristic 34 ^v indicates in the area adjacent to the speed zero ^50V a high slope, so that when starting the electric motor can set a relatively high drive torque that can be used as a breakaway torque.

In the above illustration, it is understood that when speaking of a slope of a characteristic or a characteristic section, the amount of the slope is generally meant.

Claims (15)

Drive arrangement ( 20 ) for a hand-held implement ( 10 ) for landscaping, forestry and horticulture, with an electric motor (M), a memory (A) for electrical energy, and a control device (S) for the from the energy storage (A) powered electric motor (M), wherein the electric motor (M) a specific, in particular linear characteristic ( 30 ) between the electrical current (i) received by the electric motor (M) and the rotational speed (w) of an output shaft ( 22 ) of the electric motor (M), wherein the control device (S) current limiting means ( 26 ), which limit the current (i) flowing through the electric motor (M) to a maximum value in order to protect the electric motor (M) from overloading, characterized in that the control device (S) measures the current consumption of the electric motor (M) limited to a range of low rotational speeds as a function of the rotational speed to values that are significantly smaller than the characteristic values, which for these rotational speeds from the characteristic ( 30 ) of the electric motor (M). Drive arrangement according to Claim 1, characterized that limiting the power consumption regardless of the temperature of the Electric motor (M) takes place. Drive arrangement according to claim 1 or 2, characterized in that the control device (S) of the characteristic ( 30 ) of the electric motor (M) predetermined speed range is divided into a plurality of at least three speed ranges, wherein at least in a medium speed range, a control characteristic section ( 39 . 41 . 43 ; 39 ^I . 41 ; 39 ^II ) with a lower slope than the characteristic ( 30 ) of the electric motor (M) is set up. Drive arrangement according to claim 3, characterized in that in a lower speed range, a control characteristic section ( 37 ; 37 ^I ; 37 ^II ) is arranged with a pitch which is smaller than the slope of the control characteristic section ( 39 . 41 . 43 ; 39 ^I . 41 ; 39 ^II ) in the middle speed range. Drive arrangement according to claim 4, characterized in that the slope of the control characteristic section ( 37 ; 37 ^I ; 37 ^II ) is zero in the lower speed range. Drive arrangement according to one of claims 1-5, characterized in that in an upper speed range ( 44 ; 44 ^I 44 ^II ) substantially no limitation of the current consumption takes place. Drive arrangement according to one of claims 1-6, characterized in that the control device (S) generally limits the current consumption of the electric motor (M) in the range of low speeds to values which are at least 20% smaller than the characteristic values that are suitable for these speeds from the characteristic curve ( 30 ) of the electric motor (M). Method for controlling an electric motor (M) fed from an electrical energy store (A) for a drive arrangement ( 20 ) of a portable working device ( 10 ) for landscaping, forestry and horticulture, wherein the electric motor (M) has a specific, in particular linear characteristic ( 30 ) between the electrical current (i) received by the electric motor (M) and the rotational speed (n) of an output shaft ( 22 ) of the electric motor (M), wherein the current flowing through the electric motor (M) current (i) is limited to a maximum value to protect the electric motor (M) from overloading, wherein the current consumption of the electric motor (M) in a range low speeds is generally limited to values that are significantly smaller than the characteristic values, which for these speeds from the characteristic ( 30 ) of the electric motor (M). The method of claim 1, wherein the current limit optimal efficiency. Method according to claim 8 or 9, wherein the control characteristic generated by the current limitation ( 34 ^III ) in the region of the current limiting a hysteresis section ( 37 ^III ) includes. Method according to claim 10, wherein the hysteresis section ( 37 ^III ) is designed so that when increasing the speed of a relatively high current ( 37b ^III ) and that when the speed is reduced, a relatively lower current ( 37a ^III ) is recorded. Method according to one of claims 8-11, wherein the control characteristic generated by the current limitation ( 34 ^IV ) in the area of current limiting a section ( 37 ^IV ), in which the control characteristic has a negative slope. Method according to one of claims 8-11, wherein the control characteristic generated by the current limitation ( 34 ^v ) in the field of current limiting a breakaway section ( ^50V ), in which when starting the electric motor (M) from standstill, a very high current is absorbed. Method according to one of claims 8-13, wherein the speed of the electrical parameters of the electric motor is derived. Hand-guided implement ( 10 ) for landscaping, forestry and horticulture, with a drive arrangement ( 20 ) according to any one of claims 1-7.